Most of the existing inner red-dot sighting devices use cells, such as lithium to provide power needed by the inner red-dot module (using LED as the light source) when working. The cells have limited lifetimes and should be replaced, increasing the cost. Further, during using, since the light in the outside environment changes, the current or voltage supplied by the cell should be adjusted, so as to achieve adjusting the luminance of the light emitted from the inner red-dot module. For example, when the environment luminance increases, the luminance of the light emitted from the inner red-dot module should be increased. Conversely, the luminance of the light emitted from the inner red-dot module should be decreased. Such inner red-dot sighting device relies on the power supplied by the cell day and night, increasing replacement cost for the cells. Besides the above-mentioned inner red-dot sighting device, most of the current lighting devices or auxiliary sighting devices use LED as the light source, and most of them are powered by cells which should be replaced frequently, increasing the using cost.